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The Tux3 filesystem returnsThe Tux3 filesystem returnsPosted Jan 6, 2013 3:29 UTC (Sun) by jeltz (guest, #88600)In reply to: The Tux3 filesystem returns by butlerm Parent article: The Tux3 filesystem returns
PostgreSQL has full_page_writes on by default which I assume is the setting for controlling "block image journaling". Though I am pretty certain it does not matter for making backups.
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The Tux3 filesystem returns Posted Jan 6, 2013 13:34 UTC (Sun) by andresfreund (subscriber, #69562) [Link]
full_page_writes doesn't mean that full pages are written all the time though - it means that the first time a page is touched after a checkpoint it will be logged entirely. If you have write intensive workloads the system should be configured in a way it doesn't checkpoint permanently...
The reason its on by default is that its important for consistency in the face of OS/HW crashes. Postgres' pages are normally bigger than the disks sectors and you could get into problems if e.g. one half of a page was written but the other was not and the WAL record only contains information about the one of them. As recovery always starts at a checkpoint its enough to log the page fully once after each checkpoint.
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